Crop gathering devices for collecting crops arranged in windrows can include a belt positioned along the front of the device. The belt is driven to rotate between opposed pairs of roller assemblies to convey the crops into a header that is secured to an agricultural harvester, such as a combine in which is directed along the windrow. To maintain tracking, or alignment control of the belt with respect to the crop gathering device, only the distance between the respective ends of the roller assemblies is adjustable. The belt is maintained in frictional contact with the roller assemblies by virtue of tension or increasing distance between the ends of the roller assemblies.
In operation, crops are often disproportionately positioned toward the center of the window. Due to the concentration of weight of the crop near the center of the belt, there may be insufficient friction between the belt and the rollers, resulting in “belt slippage.” Increasing the distance between the opposed rollers can result in roller deflection, resulting in inconsistent amounts of tension applied to different portions of the belt, and possibly damaging the outer edges of the belt.